feat: propagate Publish caller through all pubsub metrics

[deniseli]

Previously, only ftl.pubsub.published had the caller attribute. This PR adds caller to the rest of the pubsub metrics and also slightly restructures the topic name/ref logging to be more consistent with the rest of this file

Metric #0
Descriptor:
     -> Name: ftl.pubsub.published
     -> Description: the number of times that an event is published to a topic
     -> Unit: 1
     -> DataType: Sum
     -> IsMonotonic: true
     -> AggregationTemporality: Cumulative

NumberDataPoints #0
Data point attributes:
     -> ftl.module.name: Str(echo)
     -> ftl.pubsub.publish.caller.verb.ref: Str(echo.Echo)
     -> ftl.pubsub.topic.ref: Str(echo.echotopic)
     -> ftl.status.succeeded: Bool(true)
StartTimestamp: 2024-08-01 01:19:43.556864 +0000 UTC
Timestamp: 2024-08-01 01:20:08.558236 +0000 UTC
Value: 1

Metric #1
Descriptor:
     -> Name: ftl.pubsub.sink.called
     -> Description: the number of times that a pubsub event has been enqueued to asynchronously send to a subscriber
     -> Unit: 1
     -> DataType: Sum
     -> IsMonotonic: true
     -> AggregationTemporality: Cumulative

NumberDataPoints #0
Data point attributes:
     -> ftl.pubsub.publish.caller.verb.ref: Str(echo.Echo)
     -> ftl.pubsub.sink.module.name: Str(echo)
     -> ftl.pubsub.sink.ref: Str(echo.echoSinkOne)
     -> ftl.pubsub.subscription.module.name: Str(echo)
     -> ftl.pubsub.subscription.ref: Str(echo.sub)
     -> ftl.pubsub.topic.module.name: Str(echo)
     -> ftl.pubsub.topic.ref: Str(echo.echotopic)

Issue: #2194

[alecthomas]

This will need to have a default (or be nullable), otherwise the migration will fail on existing columns.

[deniseli]

Whoops thanks for the reminder!

[alecthomas]

How is this different to .ref above?

[deniseli]

They're the same, but the consensus in Slack (with the rest of the otel folks) was to just log both. It is possible to filter by module-only using the ref by doing a string match in datadog, but that's a little more annoying than having this attr here. WDYT? I could just remove the duplicated module attrs everywhere.

[deniseli]

Oh hmm it looks like DD's "split graph" feature doesn't support any special string matching; you have to just pick an attribute and it slices all the graphs by that. So that would be an argument to keep module in there :/